1. Field of the Invention
The present invention relates to a recording apparatus for developing an electrostatic latent image formed on an image carrying body, such as a photoreceptor, and recording the developed image on a transfer material such as paper.
2. Description of the Related Art
Conventional recording apparatuses of this type include electrophotographic devices electrostatic printers, etc. In the case of conventional apparatuses, an electrostatic latent image is formed on a photoreceptor, and a developing agent is then made to adhere electrostatically to the latent image, as a result of which a developing agent image is formed. Subsequently, the developing agent image is recorded by being transferred to paper. After image transfer, the electrostatic latent image and untransferred particles of the developing agent remain on the photoreceptor, the residual developing agent being removed by means of a cleaning device, and the latent image then removed by means of a de-electrifying device.
In recent times, there has been increasing demand for such recording apparatuses in more compact 25 form. In this connection, a method is disclosed in Published Unexamined Japanese Patent Application No. 47-11538, for example, whereby a recording apparatus is reduced in size through making use of a device which serves, as both a developing device and a cleaning device. According to this method, an electrostatic latent image is developed as a photoreceptor drum makes a first passage through the developing device, and a residual image remaining after transfer is cleaned off as the drum makes second passage therethrough.
However, because the cleaning step is effected by means of the photoreceptor drum making a second passage through the developing device, the recording speed is halved, and the recording area cannot be greater than the area of the whole peripheral surface of the drum. To obtain a greater recording area, therefore, the photoreceptor drum must inevitably be made relatively large in size, so that the apparatus cannot be satisfactorily reduced in size.
Disclosed in U.S. Pat. No. 3,649,262, on the other hand, is a method in which reduction cf the recording speed is prevented by using a developing device which can remove the residual developing agent as it develops an electrostatic latent image.
According to this method, however, charging of the photoreceptor drum, formation of the electrostatic latent image, and developing are performed with the residual image left on the drum after the transfer process. In the charging process, therefore, the latent image and developing agent image remaining on the photoreceptor drum are unexpectedly charged, and next, image exposure is effected. Accordingly, uniform charging and satisfactory formation of the electrostatic latent image cannot be insured, and the residual image in the preceding process develops superposed on a so-called ghost image. Thus, the resulting image is not clear. Such a phenomenon is liable to present itself particularly when the solid area of the image (in which the developing agent image spreads over a wide area) overlaps the residual image in the preceding process. Moreover, it sometimes is the case that a residual developing agent image itself, as well as the residual electrostatic latent image, remains as a residual image on account of insufficient cleaning, and sometimes may be transferred to the paper.
While it is preferable, from the point of view of reducing the size of a recording apparatuses, to employ, as the developing device, a one-component system using a one-component developing agent, this type of system, however, has the drawback of possessing a poor mechanical cleaning capability.
Thus, the conventional recording apparatuses cannot produce distinct images, and never permit reduction in size.